Torque control system for electric reel motors



Aug. 24, 1948. A. F. KEN YON 2,447,654

TORQUE CONTROL SYSTEI 'FOR ELECTRIC REEL MOTORS Filed June a, 1946 wrmssszs: I INVENTOR 4 7' 4 9/00 2 01? A enyan.

gym w Patented Aug 24, 1948 V TORQUE CONTROL SYSTEM FOR ELECTRIC REEL MOTORS Alonso F. Kenyon, Pittsburgh, Pa., asaignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 8, 1948, Serial No. 675,341

My invention relates generally to control systems, and it has reference in particular to tension control systems for use with reel motors. 7

Generally stated, it is an object of my invention to provide a tension control system which is simple and inexpensive to manufacture, and which is reliable and eflicient in operation.

More specifically, it is an object of my invention to provide for using a regulating generator for controlling the operation of a reel motor to maintain a predetermined tension in a strip of material which is being wound or unwound.

It is an object 01' my invention to provide for varying the torque of a reel motor to maintain a more nearly constant value 01 tension in a material during acceleration or deceleration of the material.

Another object of my invention is to provide 8 Claims. (CL 318-454) ing typeto vary the energization of the motor a tension control system which is extremely flexible in operation and readily adjustable to provide a wide range of tensions, such as are necessary with materials of different sizes and grades.

Yet another object of my invention is to provide a predetermined inertia compensating effect in a reel control system of an adjustable torque type during acceleration or deceleration, regardless of the particular torque level at which the reel motor may be operating, I

It is also an object of my invention to provide for using a separate variable bias field winding on a regulating generator controlling a reel motor for determining the particular percentage 01' full load torque at which'the motor is to operate, and for using a reference field winding which is variably energized in accordance with predetermined operating conditions of the motor to compensate for varying torque demands.

neld winding. The regulating generator has a control field winding energized in accordance withthe reel motor armature current, and a cumulative bias field winding whose energization is varied to determine at whee percentage of full load torque the motor is to operate. A differential reference field winding energized from a substantially constant voltage source has its energization varied to compensate for varying torque conditions during acceleration and deceleration.

For a more complete understanding of the nature and scope of my invention, reference may be made to the following detailed description which may be studied in connection with the accompanying drawing in which the single figure is a diagrammatic view of a reel control system embodying the invention in one of its forms.

Referring to the single figure of the drawing,

the reference numeral i0 may denote generally, a reel control system wherein a reel motor 12 having an armature 13, an interpole field winding H, and main and auxiliary field windings ii and i5, may be arranged to drive a reel ii for coiling or uncoiling a strip or material ii,

The armature l3 oij the reel motor i2 may be energized from any suitable power source, being, for example, connected to the armature is of a variable voltage main generator 2! having a field winding 2i, and driven by a motor 22. The out- It is an important object of my invention to,

provide for so controlling the regulating generator of a reel control system that the predeterminedvalue of reel motor armature current which is normally maintained, may be varied during acceleration and deceleration to compensate for inertia and maintain more nearly constant strip tension.

Yet another object of my invention is to provide for varying the energization of the reference ileld winding of a regulating generator in response to increase or decrease of the field energization of a variable voltage generator supplying energy to a motor controlled by the regulating generator.

Other objects will, in part, be obvious and will, in part, be explained hereinafter.

In practicing my invention in one of its forms, the operation of a reel motor is controlled bi! using a regulating generator'of the self-energizpower source, such as a constant potential generator 23 driven by the motor 22, through a motor-driven rheostat 25.

The rheostat 25 may comprise a movable contact arm 28 actuated by a motor 28 for variably shunting portions of a resistance element 29, which may be connected in circuit relation with the'field winding 2 I. The operation of the motor 28 may be controlled in any manner, such as by means or "raise and "lower pushbutton switches 30 and 32, which may be arranged to connect raise" and lower field windings 33 and. respectively, of the motor to the constant potential generator 23.

A booster generator 35 may be connected in circuit with the armatures i3 and i9 and driven by the motor 22 to compensate for the I. R. drop of the reel motor 12.

In order to regulate the tension in the strip of material H, a regulating generator 35 may be provided for controlling the operation of the reel motor. The auxiliary field winding l5 0! the reel motormay be connected to the constant In this instance the regulating generator 86 is' provided with several field windings. A series field winding ti. connected in circuit relation with the armature 40 and the field winding id, is utilized to substantially compensate for the masnetomotivc air gap losses and maintain the generator output under balanced operating conditions. The rheostat 38 may be adjusted to vary the slope of the resistance line of the field winding H 50 that the resistance line substantially coincides with the straight portion of the saturation curve to achieve such conditions. A control field winding 42 is used to normally oppose a ref erence field winding 43. The control field winding 42 may be energized in accordance with the armature current oi the reel motor i3. so as to be responsive to torque developed by the motor. It may, for example be connected across the interpole field windings i i and/or a series resistor 44.-

A bias field winding 45 on the. reeulatinggenera= tor is connected to be additive with respect to the control field winding 42.

The bias field winding may be connected to an excitat on source. such as the constant potential generator 23. through a field rlicostat 57 wh ch may be ut lized to control the energiza ion of the bias fie d ind n 45 for determi ing what percentage of full load toroue the reel motor is to develon. The fie d rheostat ll may be adjusted to obtain difierentoperating torque levels. dependent noon the "requirements of the particular material which is be ng handled.

In order to provide for i aintauriim. more nearly the same tension in the atria ll, regardless of the p rt cular operating conditions of the reel motor l2. the energizat on of the reference field winding t3 may be varied by control means including resistance means 48. The efiective value of the resistance means 48 may be varied depending upon whether the strip is accelerating. decelerating or running at substant ally constant speed. Since the rheostat 25 is operated to vary the volta e of the main generator 20 in order to vary the speed of the main reel motor (not shown) and hence the speed of the strip ll. the contact member 366 of the raise pushbutton switch 80 '-may, for example, be connected for shunting a portion 8a of the resistance means 48 when the pushbutton switch 3!! is depressed to operate the rheostat mo or 28 to raise the voltage oi the generator ill. The contact members 32a oi the "lower" pushbutton switch 32 may be connected to shunt a portion 48b of the resistance means when the reel motor is operating at a substantially constant speed and for effectively connecting it in circuit with the reference field winding 43 wh the reel vmotor is decelerating.

The actual torque developed by the reel motor I! thus may be varied so as to compensate for the different torque requirements due .to inertia during acceleration and deceleration. The net i be maintained more nearly at a constant value torque of the "reel motor I! which is applied to during changing operating conditions.

The control and bias field windings 42 and 45 are normally 0! the same polarity and, under normal operation, the magnetization produced by them is equal to and opposes the magnetization of the reference field winding 43, as shown by the polarity indicating arrows in red. Under these conditions, the regulating generator 36 operates, whenever an increase in the armature current of the reel motor indicates increased torque output of the motor, to strengthen the net energiza- -tion of the main field winding I4 and hence, re-

duce the output torque of the reel motor I! to .the predetermined value. By changing the operating position of the bias field winding rheostat- 41, the operating torque level of the reel motor I2 may be readily changed. If the energization oi the bias field winding 45 is reduced, the energization required for the control field winding 42 to balance the magnetization produced by the reference field winding 43 will be increased. Hence, the armature current and the operating torque level of the reel motor will be increased. As'the energization of the bias field winding 45 is increased, the energization of the control field winding 42 required to balance the eflects of the reference field winding 43 'is reduced and may even be reversed as indicated by the polarity indicating arrow in red, so that the armature current will be maintained at a lower value and the motor operates at a lower torque level. as illustrated by the following table:

Torque level control Relative Ampere Turns Per Cent Rnixd Reel Motor 0 t l R rm. mperes on IO e erence Field 3,25, 3 Field Winding g Winding 25 -l50 100 50 l50 60 100 l50 0 150 Because of the inertia of the reel and coiled strip, as well as of the inertia of other rotating parts of the system, the torque required from the reel motor i2 varies, depending upon whether the motor is accelerating, running at constant speed or decelerating. It is desirable tocompensate for the diilerence in torque requirement under different operating conditions in the same amount, independently of the particular operating torque level. By using the control resistance means 48 in conjunction with the "raise and lower pushbutton switches 30 and 32 which control the operation of the rheostat motor to raise and "lower the voltage oi the main generator 20. predetermined changes in the torque of the reel motor may be eil'ected whenever this motor is accelerated or decelerated by "raising or lowering" the voltage applied thereto.'

Since the torque level at which the reel-motor i2 operates is determined by the energization of the bias field winding 45, which is separate from the reference field winding '43, variations in the energization of the bias field winding 45 do not afl'ect variations in the energization of the reference field winding 43, which may be produced by operation of the pushbutton switches 30 and 32. Accordingly, a predetermined change of resistance in thereference field winding circuit gives the same inertia compensation, regardless of the particular torque level for which the bias field ass-1,0

s winding ll may be adjusted, as shown in the following table:

Thus, it will be seen that while operating under constant speed condition, the energlzation of the control field winding 42 will be dependent upon the armature current of the reel motor I2. An increase in armature current indicating increased tension in the strip ll increases the energization of the control field winding 42. This increases the net output of the regulating generator I8, and increases the energization of the main field winding ll of the reel motor. The reel motor thus tends to slow down and reduces the tension in the strip i1 tothe predetermined value. Should the tension decrease, the energization of the control field winding 12 is reduced, and the reel motor tends to speed up, thus restoring the predetermined tension.

6 l3 and thereby reducing the armature current required for balance. This reduces "the drag torque so as to maintain the strip tension more nearly uniform.

7 From the above description and accompanying drawing, it will be apparent that I have provided When the reel motor I! is accelerating as, for

ing amoimt to that of the reference field winding. The increased armature current produces additional torque to overcome the inertia of the moving parts including the reel, motor and coiled strip, thus, in effect, changing the calibration of the control field winding 42 and permitting the reel motor to draw a higher armature current without causing the regulating generator 36 to attempt to reduce this increased armature ourin a simple and effective manner for utilizing a regulating generator to control the operation of a winding reel or a pay-off reel. By utilizing a separate variably energized bias field winding in the manner hereinbefore described, I provide a highly flexible reel control system which is readily adaptable forhandling materials of many diflerent sizes and characteristics which may require a wide range of different values of tension. By controlling the energlzation of the reference field winding in accordance with whether the voltage of the system is being increased or decreased, to accelerate or decelerate the reel motor, compensation for inertia may be readily obtained, independently of the particular torque level at which the motor is operating. This greatly facilitates handling a wide range of operating torque levels.

Since certain changes may be made in the above described construction, and diiferent embodiments may be made of the invention without departing from the spirit or score thereof, it is intended that all the matter contained in the above description and shown in the accompanying drawing shall be considered as illustra tive and not in a limiting sense.

I claim as my invention:

1. A reel system comprising, a reel motor having a field winding and an armature disposed to be energized from a source of electrical energy, a regulating generator normally operable to effect energization of the field winding in accordance with the armature current of the motor, speed adjusting means operable to vary the voltage at which electrical energy is supplied from said source; and control means operable to vary the output of the regulating generator in accordance rent. The tension of the strip i I is, therefore,

The energi'zation of the reference field winding 42 for balancing. The torque of the reel motor is thereby reduced so as to prevent increasing the tension in the strip I! under these conditions.

While the operation of the system has been described for a winding reel, it is obvious that the system may also be used with a pay-oi! reel to unwind strip, it being only necessary to make the contact members 301) and 32a, normally closed and open, respectively, reverse the connections of the control, reference and bias field windings, and remove the rectifier 3!. Increased strip tension will then cause the control field winding I! to buck the reference field winding and reduce the energization of the field winding ll, whereby the strip tension is reduced. On accelerating, the closed contact member Iilb will open, reducing the energization of the reference field winding with predetermined operations of the speed adlusting means to eifect changes in the speed of the motor.

2. In a control system for a reel motor having an armature and a field winding, a regulating generator connected to effect energization of the field winding and having a plurality oi. field windings, circuit means connecting one of the field windings for energization in accordance with the armature current of the reel motor, circuit means including speed adjusting means operable to effect variable energization of the reel motor armature,- and additional circuit means connecting another of the field windings to a source of electrlcal energy for energization in the opposite sense, said circuit means including control means operable in response to predetermined operation of the speed adjusting means to effect a change of speed of the motor, said control means being effective to vary the torque of the motor.

3. For use in controlling a motor having an armature and a field winding, circuit means connected to apply a. variable voltage to the arma ture including adjusting means to vary the voltage, a regulating generator connected to effect energization of the field winding, said regulating generator being provided with a plurality of field windings, circuit means connected to energize one of the field windings in accordance with the load on the motor, circuit means including a variable control device connecting another of the field windings for normal energization cumulatively in different degrees to effect operation of the motor 4. For use in controlling a motor having a field ing variable impedance means in said additional circuit' means responsive to operation of the adlusting means to eiTect acceleration and deceleration of the'motor.

5. In a control system for a motor havin an armature disposed to be energized from a source of direct current voltage and a field winding, control means operable to vary thevoltage of the source, a regulating generator connected to energize said field winding having a control field winding disposed to be energized in accordance with the motor' armature current and a reference field winding normally energized at a predetermined level in opposition to said control field winding, and variable impedance means connected'in circuit relation with the reference field winding operable to vary the energization of said field winding from the predetermined level in accordance with operation of the control means to effect acceleration or deceleration of the motor.

6. A control system for a reel motorv having an armature disposed to be energized from a direct current voltage source and a field winding comprising, a regulating generator connected to energize the field winding, said generator having 'a control field winding responsive to the armature current of the motor, a bias field winding connected for variable energization to vary the ef-" fective torque of the motor and a reference field winding connected in circuit with a variable impedance device for energization in opposition to the control field winding, contro1 means operable:

to vary the voltage of the source, and additional control means operable in accordance with predetermined operation of the control means to efiect variation of the source voltage to accelerate or decelerate the reel motor to vary the impedance device to produce a predetermined change in the torque developed by the motor.

7. The combination with a. reel motor having an armature and a field winding, of means for applying a voltage to the armature, adjusting means operable to vary said voltage regulating means comprising a generator connected to energize the motor field winding and having a plurality of field windings, circuit means connecting one of said windings to a source of substantially constant voltage including a rheostat operable to vary the energization of said winding for predetermining difierent operating torque conditions, circuit means connecting another of the windings for 'cumulative energization in accordance with the armature current of the motor, additional circuit means connectingyet another oi! the field for energization i opposition to said other field windings from a substantially constant voltage source, and circuit means including a control resistor connected in circuit relation with the lastmentioned field winding and normally closed and normally open contact means operable to vary the energization of the last-mentioned field winding whenthe adjusting means is operated to raise or lower the voltage of the variable voltage source to accelerate or decelerate the motor.

8. For use with a motor having an armature energized from a variable voltage generator and a field winding, a regulating generator having anarmature connected to energize the field winding and having a plurality of field windings including a field winding of the series type, disposed to maintain the output voltage under balance conditions, circuit means including an adjustable rheostat connecting one of the field windings for energization from a source of control voltage-for determining the operating torque level, additional circuit means connecting another of the fieldcrease the voltage applied to the armature, andmeans selectively operable in response to opera-- tion of the-aforesaid means to decrease or increase the energization of said field winding.

ALONZO F. KENYON.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATESO PATENTS Name Date Alexanderson Aug. 29, 1924 Number 2,357,087 

